"Foraging is the most basic activity of animals, but details of foraging behaviour are poorly known, especially in marine animals," lead scientist Dr Yuuki Watanabe from the National Institute of Polar Research in Tokyo said.

The penguins` foraging area is largely covered by marine ice and their primary food sources include two species of krill and Pagothenia borchgrevinki - a fish whose blood contains antifreeze proteins.

The team discovered that Adelie penguins can catch krill at a rate of up to two krill per second, despite the krill`s displaying escape behaviours.

Researchers found that the camouflage defence of the fish P borchgrevinki didn`t work with foraging Adelie penguins.

The penguins were regularly able to capture the fish from below - the direction from which the fish is camouflaged against the backdrop of marine ice.

"Previously some researchers attached video cameras to marine animals to observe their foraging behaviour, but this was just a few hours.

"In other studies, researchers attached various sensors to marine animals to record indirect signals of prey capture. This method lasted for long periods, but has never been validated in the field," said Watanabe.

To overcome these difficulties, the Japanese scientists decided to use a combination of video footage and indirect signals.

"We recorded both movies and indirect signals, successfully validating the indirect signals using video footage," said Watanabe.

"We assumed that penguins move their heads relative to their body when they capture prey, this was confirmed by the footage," he said.